The Obama administration and its European allies are quietly preparing for a possible new round of international nuclear talks with Iran in the coming weeks, sources consulted on the prospective meeting say.

The prospective talks would be hosted by Turkey--and the preparations around them have taken shape amid heightened tension and heated rhetoric between the West and Iran, as Iran lashes out at planned new American and European sanctions that would choke off a key source of Iran's revenues from oil exports.

European and American officials say that no meeting has yet been agreed--and that a formal meeting date won't be set in the absence of firm commitments in writing from Iran pledging to engage in serious negotiations.

There will be no meeting "unless and until" the Iranians send a "letter that makes clear their intentions to engage seriously," a U.S. administration official told Yahoo News Wednesday. American officials haven't seen such a letter to date.

Michael Mann, a spokesman for European Union foreign policy chief Catherine Ashton, echoed the same message.

"Before we can do anything, we need Iran to respond on the substance of our proposals," Mann told Yahoo News Wednesday via email.

The account from other sources indicating that a meeting is tentatively set for the Turkey-hosted talks in the next few weeks "is not true," he added.

Turkish Foreign Minister Ahmet Davutoglu met with his Iranian counterpart, Ali Akbar Salehi, in Tehran last week, and formally announced his country's offer to host the next round of international Iran nuclear talks.

Iran watchers say they think a meeting is likely to materialize--in spite of the considerable diplomatic difficulties involved in obtaining Tehran's written assent to the plan for the talks. Those difficulties have grown nearly comic at times. Ashton first issued the meeting proposal back in October; Turkey's Davutoglu re-delivered the proposal on his Iran visit last week, apparently to firmly nudge Iran to send the requisite RSVP. Iran in turn reportedly insisted that it did send off a formal response to Ashton on December 31. But staffers at Ashton's office told Yahoo News Tuesday that they checked the system again this week, only to find there is no letter.

Several veteran U.S. Iran analysts who consult closely with the Obama administration say they are growing increasingly worried about the risk of possible military confrontation between Iran and the United States.

Some analysts contend, in essence, that the Obama administration has become so focused on demonstrating toughness toward Iran that it has lost sight of how to achieve its desired end goal: persuading Iran to curtail aspects of its nuclear program. Exhibit A in this case is the push to implement newly passed U.S. legislation sanctioning Iran's Central Bank. This new measure--quietly opposed by the administration but passed by the Senate 100-to-0 and signed into law early this month--would effectively threaten Iran's ability to get compensation from foreign entities that purchase its oil. And the Obama administration has energetically set about enlisting countries around the world to comply--negotiating with oil supplying-nations and major Iran oil consumers in Asia to try to secure alternative oil-sources, while averting a spike in international oil prices. However, amid this full court press, some analysts say, American policymakers have spent far too little energy and attention on establishing negotiating strategies, channels and contacts to bolster chances of achieving a diplomatic resolution with Iran over its nuclear program.

The U.S. "decision to outlaw contact with Iran's central bank puts the United States' tactics and its long-standing objective--a negotiated end to Iran's nuclear ambitions--fundamentally at odds," Suzanne Maloney, a former State Department Iran official now with the Brookings Institution, wrote in Foreign Affairs this month. Washington "cannot hope to bargain with a country whose economy it is trying to disrupt and destroy. As severe sanctions devastate Iran's economy, Tehran will surely be encouraged to double down on its quest for the ultimate deterrent."

The upshot? Washington's "embrace of open-ended pressure means" the United States has effectively backed itself into a dead-end "policy of regime change," Maloney continued.

Obama faces both a domestic "political challenge and there are also divisions within the administration, so they don't know what the end game is," a former State Department official who requested anonymity to speak more freely told Yahoo News Wednesday. "What we have now is the folks in Tehran increasingly starting to believe the United States doesn't know what it wants its endgame to be--or that its endgame can change. Here we are at a position where both sides find themselves boxed in."

The 2012 presidential campaign has further increased domestic political pressure on the Obama administration to demonstrate toughness and resolve in its dealings with Iran--while downplaying prospects for a diplomatic settlement. The Obama White House's drift toward a more hawkish posture also may reflect the pressure, in some observers' eyes, to ward off any Israeli preemptive strike on Iran's nuclear facilities. Iran watchers agree that the Pentagon takes the prospect of such a strike from Israel quite seriously.

Meanwhile, Obama administration officials counter that the sticking point in negotiations has to do with Iran's behavior--and with Iran's own internal political tensions and dysfunctions. They deny that the White House has embarked on any policy of regime change in Iran.

"The fundamental question is whether because of all the factional infighting in Iran, whether they are even capable of making a decision on their nuclear program," a former senior administration official told Yahoo News. He pointed to Iran's initial 2009 acceptance of a nuclear fuel swap deal--a provisional bargain that broke down after drawing heavy criticism from the domestic political rivals of Iranian President Mahmoud Ahmadinejad.

"So the first question is whether Iran is capable of striking a deal," he said. "The counter-argument is that, if the Iranians are incapable of responding to incremental increases in pressure, maybe we have to hit them with something so threatening" that the Supreme Leader makes a decision.

"Obviously sanctions . . .are not an end in themselves," Deputy Secretary of State Bill Burns said in an interview Tuesday in Turkey with the Anadolu news service. "They are a means to an end to make clear to the Iranian leadership that it must live up to its international responsibilities and obligations."

"We have made clear . . . that we are prepared to engage in serious negotiations with Iran on international concerns about its nuclear program," Burns continued. "But we are also, at the same time, deeply concerned about Iran's failure to live up to its international obligations. … We want to work with Turkey and with our other partners to try to make this clear to the Iranian leadership."

Burns traveled to Turkey this week to further discuss the recent conversations between Iranian and Turkish officials. The United States is effectively calling on Turkey to help play postman and mediator between Iran and the West--and thereby grease the wheels for possible new nuclear discussions. Notably, Burns' visit to Ankara was immediately followed by that of Iran parliament speaker and former Iran nuclear negotiator Ali Larijani, a close ally of Supreme Leader Ayatollah Khamenei.

"Thank God the Turks were willing to put their feet in the fire again to do this shuttle diplomacy, which is high risk," the former State Department diplomat said. "At the end of the day, there will be negotiations in Istanbul at the end of the month. They will go down. And both sides are doing whatever they can to build up leverage and protect themselves politically at home."

"What we have been saying to Iran is that there has got be a confidence building measure that emerges out of the next round of negotiations," said Patrick Clawson, deputy director of research at the Washington Institute for Near East Policy, in an interview with Yahoo News Tuesday.

"I think it's heading towards confrontation," Clawson said. "The whole point from the beginning is if we put pressure on the regime, the Iranians will crack at some point."

So far, at least, there's little sign the strategy is yielding the desired result. The Iranians to date have responded to the prospect of the tightened financial sanctions on the country's oil sector with an announcement of the launching of operations at the fortified, underground Fordo nuclear enrichment facility--together with sporadic threats to close the Strait of Hormuz. "The Iranians are screaming and yelling and upset and threatening," Clawson said.

So why isn't that a sign that the U.S. strategy is failing?

"It's a lot better to have a fight" that Iran provokes, Clawson replied, before adding: "Better to enter World War II after Pearl Harbor, and World War I after the sinking of the Lusitania."